Induction heating detachable work coil



Aug. 31, 1965 H. B. HUNTING, JR 3,204,074

INDUCTION HEATING DETACHABLE WORK COIL Filed April 25, 1963 I 4 F|e.1

r 8 P PIC-1.5 L," W .L 5' f2 9 4 INVENTOR.

HAROLD B. HUNTING,JR

7 Agent United States Patent 3,204,074 INDUCTION HEATING DETACHABLE WORK COIL Harold B. Hunting, Jr., Van Nuys, Calif., assignor to Lockheed Aircraft Corporation, Burbank, Calif. Filed Apr. 25, 1963, Ser. No. 275,716 2 Claims. (Cl. 21910.79)

This invention relates to a high frequency induction heating apparatus and more particularly to a detachable work coil for induction heating.

I-Ieretofore coils which areutilized for high frequency induction heating have been generally of two types. In one type the coil or coils are continuous loops and the work piece to be heated is placed within the heating zone. In another type, the coil or coils are usually jointed or segmented and are assembled around the work piece to be heated. The present invention primarily is of the second type.

Jointed coils generally have objectionable resistance introdueed at the pivots or contact areas which has an adverse elfect on the efiiciency of the inductive heating. As is well-known the conductivity of the conductor for induction-heating coils must be at least ninety percent or better, affording a continuous passage of electrical current.

Therefore, an object of the present invention is to provide a detachable coil overcoming one or more disadvantages of presently known coils of this type.

Another object is to provide an induction heating coil for quick removal from the work piece.

A further object of the invention is to provide a coil having maximum electrical contact of the work coil to the coil holder.

These and other objects will become apparent from the following detailed description and the accompanying drawings in which:

FIGURE 1 is a side view of a preferred embodiment of the invention,

FIGURE 2 is a plan view of the invention illustrating a double coil configuration,

FIGURE 3 is a front view of FIGURE 2.

With reference to FIGURE 1, a loop portion 1 has a pair of parallel extensions intersecting the loop as illustrated. The extensions 2 are held in rigid electrical contact to the sides of the coil leads 3 by means of a suitable clamp such as the spring clip 4. The coil leads 3 are maintained in a spaced apart relationship by means of the spacer 5, which may be of any suitable insulation material. The leads may pass through a 90 transition to a conventional mounting block for connection to a high-frequency generator.

The ends of the leads are provided with a curvature as at 6 which matches the curvature of the loop. The relatively large surface of the parallel extensions of the loop provide a maximum electrical contact area. The leads may be hollow as indicated by the dotted lines with an external connection 7 near the ends of the leads for circulation of a coolant such as water or gas. If desired, the loop may be formed of a hollow tube for circulating the coolant through the loop by utilizing a seal between the lead and the loop extension in accordance with standard practice. While an external connection 7 between the leads has been indicated in the drawings, it should be understood that a non-metallic connection may be pro- 3,204,074 Patented Aug. 31, 1965 vided directly between the leads by utilizing a water or gas tight seal.

FIGURES 2 and 3 illustrate the invention for series double coil operation, it being understood that additional coils may be added without departing from the scope of the invention. As illustrated, the leads 3' from the generator may be held in a two piece insulation block 10 and spaced laterally and vertically from each other as indicated in FIGURE 3. The bars 9 have holes drilled for water passage and are connected by the crossover tube 8. The bars 9 are held rigidly in the block 10 along with the conductive leads 3' to provide contact surfaces for the extensions 2 on the coil 1. In FIGURE 3, cooling water circulates from, say, the upper right hollow conductive lead 3' through the external connection 7 through the lower right bar 9, crossover tube 8, the upper left bar 9, external connection to the lower left conductive lead 3'. It is also evident that the crossover tube electrically connects the two coils in series. The loop portion 1 and extensions 2 have been omitted from FIGURES 2 and 3 for purposes of clarity.

As illustrated the detachable coil is proportioned for brazing standard sleeve connector joints to tubing, where the distance between the parallel extensions approximates the diameter of the tubing and the internal diameter of the loop is determined by the diameter of the connector and the degree of coupling desired. It is of course understood that the loop may be shaped in the usual manner depending on the configuration of the work piece and the heating pattern required.

For a brazing operation, for example, of fittings or conplings to a tube, the coil portion 1 is removed from the lead portion 3 and with the ends of the leads 3 adjacent the tube the parallel extensions are slipped over the tube and onto the leads as in the drawings and the clamp tightened to make a firm electrical contact. The assembled coil is then adjusted over the brazing area of the fitting and the high frequency power (not shown) is applied. It is readily apparent that disassembly and positioning at the next fitting to be brazed is accomplished by merely pulling the coil from the leads, moving to the next position and repeating the assembly as above.

Thus, it is believed obvious that the detachable coil as described has many advantages over the conventional two piece coil structure, and particularly in providing a detachable loop without hinge joints and with maximum electrical contact area. Furthermore, the expense of manufacture of the present invention is greatly reduced.

While a specific embodiment of the invention has been shown and described it should be understood that certain alterations, modifications and substitutions may be made to the instant disclosure without departing from the spirit and scope of the invention as defined by the appended claims.

What is claimed is:

1. A work coil for induction heating said coil having at least one turn comprising a loop portion, a pair of parallel members spaced apart a distance approximating the dimensions of a work piece which is to be heated and intersecting said loop portion and integral therewith, a pair of electrical conductors positioned between said members and in intimate electrically conductive contact therewith, insulation between said conductors, the ends of said conductors being shaped so as to have the same curvature as the internal curvature of the loop portion, the ends of said conductors together with said loop portion defining 3 4 substantially a full electrical turn of said coil and means 2,751,481 6/56 Blok et a1 21910.79 for maintaining said extensions in electrical contact with 2,759,085 8/56 Van Iperen 219-10.79 X said conductors.

2. T he coil as defined by claim 1 and further including FOREIGN IiArFENTS means fo Cooling said 1 5 613,322 11/48 Great Britain.

References Cited by the Examiner 980873 5/51 France UNITED STATES PATENTS RICHARD M. WOOD, Primary Examiner.

2,515,874 7/50 Hoyler et al. 21910.79 X 

1. A WORK COIL FOR INDUCTION HEATING SAID COIL HAVING AT LEAST ONE TURN COMPRISING A LOOP PRTION, A PAIR OF PARALLEL MEMBERS SPACED APART A DISTANCE APPROXIMATING THE DIMENSIONS OF A WORK PIECE WHICH IS TO BE HEATED AND INTERSECTING SAID LOOP PORTION AND INTEGRAL THEREWITH, A PAIR OF ELECTRICAL CONDUCTORS POSITIONED BETWEEN SAID MEMBERS AND IN INTIMATE ELECTRICALLY CONDUCTIVE CONTACT THEREWITH, INSULATION BETWEEN SAID CONDUCTORS, THE ENDS OF SAID CONDUCTORS BEING SHAPED SO AS TO HVAE THE SAME CURVATURE AS THE INTERNAL CURVATURE OF THE LOOP PORTION, THE ENDS OF SAID CONDUCTORS TOGETHER WITH SAID LOOP PORTION DEFINING SUBSTANTIALLY A FULL ELECTRICAL TURN OF SAID COIL AND MEANS FOR MAINTAINING SAID EXTENSIONS IN ELECTRICAL CONTACT WITH SAID CONDUCTORS. 